Oil soot handling system

ABSTRACT

Valuable metals, particularly vanadium, may be recovered from oil soot by firing crude oil to produce oil soot, collecting the soot, and recycling the collected soot for refiring until substantially all of the soot is converted to slag. The recycling of the collected soot is accomplished by the use of at least one air eductor to provide the motive power for pneumatically recycling the collected soot. During the recycling, the soot must be maintained at a temperature above its dew point, and wetting of the oil soot must be avoided.

United States Patent [191 Peacock OIL SOOT HANDLING SYSTEM [75]lnventor: Wallace D. Peacock, Kennett Square, Pa.

[73] Assignee: Ecolaire Incorporated, Philadelphia,

[22] Filed: Apr. 10, 1972 [211 Appl. No.: 242,517

[52] US. Cl 75/24, 75/25, 75/84 [51] Int. Cl C2lb 3/04 [58] Field ofSearch 75/24, 25, l, 84

[56] References Cited UNITED STATES PATENTS 3,579,328 5/l97l Aas 75/24[451 Apr. 30, 1974 Primary Examiner-L. Dewayne Rutledge AssistantExaminer-Peter D. Rosenberg Attorney, Agent, or Firm--Seidel, Gonda &Goldhammer ABSTRACT Valuable metals, particularly vanadium, may berecovered from oil soot by firing crude oil to produce oil soot,collecting the soot, and recycling the collected soot for refiring untilsubstantially all of the soot is converted to slag. The recycling of thecollected soot is accomplished by the use of at least one air eductor toprovide the motive power for pneumatically recycling the collected soot.During the recycling, the soot must be maintained at a temperature aboveits dew point, and wetting of the oil soot must be avoided.

9 Claims, 2 Drawing Figures T0 FURNACE 0R TRANSFER 0R STORAGE TANKPATENTEDAPR 30 mm FIG.

TO FURNACE 0R TRANSFER 0R STORAGE TANK F/G. Z

1 OIL SOOT HANDLING SYSTEM BACKGROUND OF THE INVENTION The presentinvention relates to an oil soot handling system. More particularly, thepresent invention is directed to an improved method for recycling oilsoot in the process for recovering valuable metals, particularly ofvanadium, from the oil soot.

The large utilities burn low grade oils, such as refinery residues andnon-treated crude oils. They have discovered that many South Americancrudes, notably oils originating in Venezuela, have a very high contentof vanadium. If the oil ash from Venezuelan crude oil is recycledthrough the burner to burn off all of the carbon, so that the remainderof the ash forms a slag, the resulting slag contains about 13 to 15weight percent of vanadium which can then be recovered quite profitably.

Unfortunately, up until the present time there have been considerableproblems with the handling of vanadium bearing oil soot. Oil soot, whichis the ash obtained from the flue of an oil burner, is far moredifficult to handle than fly ash, which is the ash obtained from burningcoal. Thus, the oil soot or ash is much finer in particle size and muchstickier, so that it tends to compact and aggregate when handled.Attempts have been made to wet the oil soot with water so as tofacilitate its handling. However, the presence of water has been foundfatal to the recovery of vanadium from the oil soot. Furthermore, theoil soot is highly hygroscopic, and as it is cooled it rapidly absorbswater, which again is fatal to the recovery of vanadium.

A typical chemical analysis of oil ash from Venezuelan crude oil withmagnesium salt additives is as follows:

Percent Carbon C 12.0 (may be higher) Silica SiO, 3.0 Iron oxide Fe O3.0 Vanadium pentoxide Va,O 21.0 Vanadium Va 12.0 Calcium oxide CaO 2.0Magnesium oxide MgO 27.0 Sllltfltate SO A typical breakdown of the sizesof the dust particles from the oil burner as they enter the collector isas follows:

As can be seen from the table of typical chemical properties above, theoil soot obtained directly from the oil burner contains a highpercentage of carbon black, which may range from about to 30 percent ofthe soot, and which must be removed to concentrate and recover thevanadium. Also, due to the small particle sizes of the oil ash, as shownin the above physical analysis, it is apparent that the stream of fineoil soot particles is highly abrasive.

In the past, a number of systems have been proposed for the pneumatichandling of oil soot for conveying between the oil soot collector andthe re-entry to the burner or storage facilities. However, such systemshave had a number of serious disadvantages. For example, vacuum systemsusing conventional materials handling valves', while simple, low in costand suitable for wet disposal methods, generally require major systemsmodifications and elaborate collecting and filtering protections for thevacuum producers, and are not generally suitable for continuousoperation.

Pressure systems using rotary (star) feeders require special precautionsto avoid oil soot sticking in rotor pockets and tight seals between therotors and seats. Also, system pressures are generally limited to 3psig. Pressure systems using air locks have a number of advantages butare high in cost due to complex controls, high maintenance costs andhigh initial equipment cost. Finally, combination vacuum-pressuresystems, using centrifugal fans, while simple in operation and low ininitial cost, have extremely high maintenance problems in most cases dueto the abrasive material passing through the fan blades. Such systemsalso require a careful balance between the vacuum side and the pressureside.

BRIEF SUMMARY OF THE INVENTION The above and other disadvantages of theprior art are overcome by the method of the present invention in whichat least one air eductor is used to provide the motive power forpneumatically recycling the collected soot in a process for recoveringmetals from oil soot. The soot is collected and recycled for retiring.This method is particularly directed to processes in which vanadium isthe metal to be recovered from the soot after the soot is retired andsubstantially converted to slag.

According to the method of the present invention, it is necessary thatthe oil soot be maintained at a temperature above its dew point, bothduring recycling and storage (in the case where the soot is not directlyrecycled to the oil burner). It is also necessary that wetting of theoil soot with water be avoided.

BRIEF DESCRIPTION OF DRAWINGS For the purpose of illustrating theinvention, there is shown in the drawings a form which is presentlypreferred; it being understood, however, that this invention is notlimited to the precise arrangements and instrumentalities shown.

FIG. I is a sectional side elevation view of an air eductor for use inthe method of the present invention;

FIG. 2 is a fragmented schematic view in perspective of a suitablesystem for employing air eductors according to the method of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG.1, there is shown an air eductor, generally designated 10, suitable foruse in the present invention. Air eductor 10 consists of two main parts,a body 12 and a tail casing 14, which are fastened together, such as bybolts or machine screws 16, for ease in disassembling.

The body 12 of the air eductor comprises a suction inlet 18 throughwhich the material to be conveyed, in this case oil soot, enters the aireductor. The body 12 is also provided with a nozzle 20 which serves todirect the stream of air or other conveying fluid into the throat 22 ofthe air eductor. The nozzle 20 is held in the body 12 by a nozzleretaining ring 24. Pipe plugs 26 and 28 are also provided in the body 12in the wall of the suction inlet 18 and at the bottom of the bodyportion. These pipe plugs allow easy access to the interior of the aireductor body for cleaning or clearing blockages of oil soot in the aireductor.

The throat 22 of the air eductor comprises a venturi shaped orificewhich begins in the body 12 of the eductor at about the apex of thenozzle 20 and is primarily held in place by the tail casing 14. Due tothe contact of the interior of the throat with high velocity abrasiveparticles of oil soot, the throat is easily replaceable and ismanufactured of a high abrasion resistant material, such as Ni-hard, atrademark for an abrasion resistant cast iron containing 4.5 percentnickel, 1.5 percent chromium and 1.5 percent manganese.

Although the air eductor may be provided in various sizes, suitablerepresentative dimensions for the air eductor 10 shown in FIG. 1 may be:overall length 10% inches, diameter of throat exit 2 inches, anddistance from center line of nozzle to be beginning of suction inlet 3%inch. Other dimensions in FIG. 1 are roughly to scale.

The air pressure of the motive air supplied to the air eductor willdepend on how far it is desired to convey the oil soot. For the aireductor whose dimensions are given above, it is contemplated to use 1 l0SCFM air at 18 lbs. per square inch gauge and 300 F. Generally, in orderto maintain the oil soot above its dew point during the recycling, theair supplied to the nozzle of the eductor must be heated to at least 300F. Also, the air should be provided at a pressure of at least psig and avelocity of at least 3,000 feet per minute.

Referring now to FIG. 2, the operation of the air eductor in the processof the present invention, will now be described. The crude oil,particularly Venezuelan crude, is fired or burned in a conventionalfurnace or burner (not shown). The oil ash or soot is then collected orretrieved by anyone of a number of conventional means (not shown), whichmay suitably include Cottrell-type electrostatic precipitators, cycloneseparators, filter bags, or combinations of the foregoing. From any ofthese collectors, the oil soot then passes into dust hoppers, one ofwhich is indicated at 30 in FIG. 2.

Each dust hopper 30 may be suitably connected to an air eductor 10 bymeans of a lever operated three-way knife gate valve 32, which is usedfor draining or washing down the dust hopper 30. The three-way valve isconnected to the upper flange 34 which surrounds the suction inlet 18 ofthe eductor. The oil soot is sucked from the dust hopper 30 through thethree-way valve 32 into the suction inlet 18 of the eductor by therapidly moving stream of air which is provided through the eductornozzle and directed into the eductor throat 22. Where the oil soot issupplied from economizer or preheater hoppers, it is preferred toprovide a cinder feeder (not shown) between each hopper and air eductorfor the purpose of sizing the oil soot prior to entry into eductor.

Motive air for the eductor is supplied by a suitable blower 36, such asa positive displacement rotary compressor. The air from the blower ispassed through electric or steam heaters 38 to raise the temperature ofthe air to a sufficient degree to maintain the oil soot above its dewpoint during the recycling. The heated air then passes from the heaters38 through suitable valved piping 40 into a common supply header 42,from which it is provided through suitable conduits 44, 44 and 44" to aseries of air eductors l0, 10, etc. The use of a plurality of oil soothoppers and air eductors, arranged in parallel, has the advantage thatif one air eductor should require maintenance, material can still beremoved by the remaining eductors, thus reducing the possibility of aboiler outage. Such an arrangement is also specially suitable where oilsoot must be removed from numerous points of collection and dischargedinto a transfer tank and storage silo.

The motive air and entrained oil soot leave the eductors l0, 10, etc.through conduits 46, 46' and 46" and enter manifold 48. The oil soot andmotive air then pass through valved recycling line 50, either for directre-injection to the oil burner or furnace (not shown) or for temporarystorage in a transfer tank (not shown). Where the oil soot is recycledto a transfer tank, it may be intermittently rapidly removed to astorage silo, from which the oil soot may be subsequently reinjecteddirectly into the furnace for reburning or refiring. It is usuallynecessary to recycle the oil soot to the furnace at least twice forrefiring in order to burn off as much of the carbon black as possibleand substantially convert all of the oil soot to slag, from which thevaluable metal such as vanadium may be recovered.

It will be understood that all pipe lines and eductors in theabove-described system should be well insulated to reduce heat lossesand thereby lessen the chances of the temperature of the oil sootfalling below the dew point. Similarly, any transfer tanks or storagesilos must be similarly insulated, and may even need to be heated ifmore than momentary storage is contemplated. This is necessary toprevent agglomeration and sticking of the oil soot while in the pipes ortanks. It is also preferred that all parts which come in contact withthe high velocity abrasive oil soot particles be manufactured of a highabrasion resistant material, such as Nihard, and be easily replaceable.

It will be seen from the above description that the use of air eductorsaccording to the method of the present invention for pneumaticallyconveying small volumes of abrasive oil soot particles from dust hoppersfor relatively short distances has a number of important advantages oversystems of the prior art. Thus, since the air eductors are staticdevices having no moving parts, they are ideally adapted for continuousoperation with a minimum of maintenance problems and costs. Secondly,air eductors are relatively low in initial cost compared to conventionalmaterials handling valves, star feeders or air locks. Thirdly, with aireductors the temperature of compression is usually sufficient to conveythe oil soot without introduction of additional heat from outsidesources. Moreover, satisfactory operation of an eductor system does notdepend on the exact tolerance and balance required by other conveyingmedia.

Furthermore, air eductors pull oil soot and flue gas from hoppers sothat there is no leakage of air into the hoppers which will upsetprecipitator efficiency. The latter is a serious problem in most systemsusing precipitators due to the low grain loading of flue gas. Probablythe only significant disadvantage of air eductor systems is the highpower requirement compared to some other conventional systems.Continuous operation is also mandatory unless metering equipment isadded to each eductor.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing specification as indicating the scope of theinvention.

I claim:

1. In a method for handling oil soot in the recovery of metals therefromcomprising firing crude oil to produce oil soot, collecting the soot,and recycling the collected soot to means for retiring the soot, theimprovement comprising providing a stream of motive air for recyclingthe oil soot, passing said stream through a nozzle in at least one aireductor to create a suction which sucks the soot into the air eductorwhereby the soot becomes entrained in the stream of air, andpneumatically conveying the entrained soot in the stream of air to meansfor retiring the soot, said soot being maintained at a temperature aboveits dew point during the 6 recycling.

2. A method according to claim 1 wherein the soot is retired untilsubstantially all of the soot is converted to slag.

3. A method according to claim 2 wherein the primary metal to berecovered from the slag is vanadium.

4. A method according to claim 1 wherein the motive air supplied to theair eductor is preheated to a degree sufficient to maintain the sootabove its dew point during the recycling.

5. A method according to claim 1 wherein wetting of the oil soot isavoided.

6. A method according to claim 2 wherein the soot is recycled at leasttwice to a furnace which is used for tiring and refiring the soot.

7. A method according to claim 1 wherein the collected soot is firstconveyed to storage means prior to refiring.

8. A method according to claim 4 wherein the heated air is supplied tothe air eductor at a pressure of at least 15 psig and a velocity of atleast 3,000 feet per minute.

9. A method according to claim 1 wherein the collected oil soot is fedto a plurality of air eductors arranged in parallel and provided with acommon source of motive air for recycling the collected soot.

2. A method according to claim 1 wherein the soot is refired untilsubstantially all of the soot is converted to slag.
 3. A methodaccording to claim 2 wherein the primary metal to be recovered from theslag is vanadium.
 4. A method according to claim 1 wherein the motiveair supplied to the air eductor is preheated to a degree sufficient tomaintain the soot above its dew point during the recycling.
 5. A methodaccording to claim 1 wherein wetting of the oil soot is avoided.
 6. Amethod according to claim 2 wheRein the soot is recycled at least twiceto a furnace which is used for firing and refiring the soot.
 7. A methodaccording to claim 1 wherein the collected soot is first conveyed tostorage means prior to refiring.
 8. A method according to claim 4wherein the heated air is supplied to the air eductor at a pressure ofat least 15 psig and a velocity of at least 3,000 feet per minute.
 9. Amethod according to claim 1 wherein the collected oil soot is fed to aplurality of air eductors arranged in parallel and provided with acommon source of motive air for recycling the collected soot.